1. Field of the Invention
Embodiments of the present invention relate to an automatic sheet feeder to automatically feed and convey a sheet for an image reader to read image data formed on the sheet so as to later perform image forming in an image forming apparatus.
2. Description of the Related Art
Related-art automatic sheet feeders, in which a sheet that is set on a sheet setting unit with a movable cover attached thereto is detected by a sheet detecting unit before being fed and conveyed by a sheet feeding unit, are generally known in the market and are detachably attachable to an image forming apparatus such as a copier and a facsimile machine or an image reading device such as a scanner.
An automatic document feeder (ADF) generally serves as an automatic sheet feeder. Many automatic sheet feeders generally include a feeler to detect whether or not a sheet is set on the sheet setting unit provided therein. When the sheet is set on the automatic sheet feeder, the feeler rotates to switch a state of a photosensor between ON and OFF. The sheet detecting unit may include a feeler that serves as an actuating member and a sensor that detects whether any sheet is set on the automatic sheet feeder according to movement of the feeler. The feeler is movably attached to an upper cover that covers a housing of the automatic sheet feeder from above.
In the automatic sheet feeder having the above-described configuration, when a paper jam occurs and the sheet stops at a sheet feeding portion, a user opens the cover to remove the jammed paper or sets the document in the sheet feeding unit again before closing the cover.
At this time, in a related-art automatic sheet feeder, when the cover is opened for paper jam handling or maintenance and is then closed with a sheet or sheets remaining on a sheet setting unit, the feeler abuts against the sheet(s) on the sheet setting unit, which can damage the sheet(s) and/or to the feeler itself. In a case where the feeler is configured to have enough of a clearance to enable it to smoothly retreat from the surface of an uppermost sheet of the sheets, such damage can be avoided even if the feeler abuts against the sheets. However, a downward slope of a guide face of the sheet feeding unit before an entrance of a sheet separation portion for the purpose of automatically separating the sheets reliably hinders the feeler from moving away from the sheets when it contacts the sheets.
Further, a support for the feeler requires a specific positional arrangement for proper detection of the existence of the sheets on the sheet setting unit. In addition, due to space limitations, the position of the support for the feeler cannot be shifted enough for the feeler to recede from the sheets easily. Therefore, it is difficult to prevent damage to the sheets and/or the feeler itself caused by the feeler inexpensively, that is, without providing extra parts or components.
To address the above-described drawback, Japanese Patent Application Publication No. 2003-095480 (JP-2003-095480-A) discloses a configuration in which a feeler is linked with an upper cover to move with opening and closing of the upper cover so as to prevent the feeler from damaging the sheets and the feeler itself.
However, Japanese Patent Application Publication No. 2003-095480 (JP-2003-095480-A) uses a linking mechanism to link the movement of the upper cover with the feeler, and therefore a large number of parts and components are required. Accordingly, the goal of providing a low-cost mechanism of the automatic sheet feeder to prevent damage to sheets and a feeler cannot be achieved.